According to a known movable grille shutter for a vehicle, in order to prevent poor combustion caused by an overcooled radiator within an engine room, a grille opening portion through which ambient air is taken in is operated to be opened or closed. For example, such grille shutter includes a plurality of fins provided at a base frame so as to be freely rotatable in such a way that the fins are connected to each other by an interlocking arm, and the interlocking arm is connected to a link mechanism that is configured by a driving arm, formed so as to include a long through hole, and a pin arranged so as to inserted into the long through hole. In this configuration, the driving arm is rotated by a drive source such as a motor in order to operate the fins so as to open or close the grille opening portion (for example a movable grille shutter disclosed in JP58-139519U).
Further, the driving force from the drive source may be decelerated by a combination of worm and spur gears and then be selectively transmitted to two movable members through an one-way clutch, in order to actuate one movable member, while stopping actuation of the other of the movable members (for example a movable grille shutter disclosed in JP64-18744A).
According to the movable grille shutter disclosed in JP58-139519U, in a case where the grille shutter is provided at a lower portion of a bumper, when the vehicle is driven through a puddle on a road surface, because an overload caused by water pressure acts on the fins and the driving force transmitting members, the overload acting on the fins is transmitted to the fins and the members for transmitting the driving force, accordingly the fins and the driving force transmitting members may break due to pressure.
Further, according to the grille shutter disclosed in JP64-18744A, although the one-way clutch is used at the movable grille shutter, such clutch does not function to support the overload acting on the fins, accordingly the fins and the members for transmitting the driving force may break due to the overload acting on the fins.
A need thus exists to provide a movable grille shutter for vehicle, which is not susceptible to the drawback mentioned above.